This invention relates to antimony pentoxide dispersions and to the use of same to provide flame retardancy to acrylic fibers.
Antimony pentoxide sols have heretofore been employed commercially to provide flameproofing or flame retardancy to various articles. For example, Nyacol Products, Inc., assignee of this invention manufactures and sells under the trade designation: ADP 494 a polar solvent-dispersible colloidal antimony pentoxide powder.
The patent literature is also replete with reference to antimony pentoxide flame retardants. While not intended to be a complete survey of such references in the patent literature, the following U.S. patents may nevertheless be taken as being illustrative: U.S. Pat. No. 3,676,362 issued to Yates; U.S. Pat. No. 3,860,523 issued to Petrow et al.; U.S. Pat. No. 3,873,451 issued to Cumbo et al.; U.S. Pat. No. 4,017,418 issued to Crompton et al.; U.S. Pat. No. 4,028,266 issued to Langere et al.; U.S. Pat. No. 4,051,064 issued to Crompton et al.; U.S. Pat. No. 4,285,900 issued to Cazzaro et al.; U.S. Pat. No. 4,348,301 issued to Crompton et al.; U.S. Pat. Nos. 4,589,997, 4,608,198 and U.S. Pat. No. 4,770,813 issued to Watanabe et al.; U.S. Pat. No. 5,008,036 issued to Crompton, et al.; U.S. Pat. No. 5,182,048 issued to Kintz and the instant Applicant, David L. Catone and assigned to Nyacol Products, Inc.; and U.S. Pat. No. 5,314,530 issued to Wierer et al.
Of these patents, U.S. Pat. No. 5,182,048 issued to Kintz and the present Applicant as joint inventors; and U.S. Pat. No. 5,008,036 are considered to be the most relevant to the present invention and further background discussion will accordingly be devoted to these two patents.
The '048 patent is directed to the task of providing improved dispensibility in polar solvents of colloidal pentoxide powders which had previously been prepared by admixing colloidal antimony pentoxide, phosphoric acid and a suitable ethoxylated fatty acid amine and then drying in air to an adsorbed moisture content of no greater than three percent.
As disclosed therein, this task is solved by the steps of: (1) forming a sol consisting of antimony pentoxide sol and phosphoric acid; (2) concentrating the sol until the concentration by weight of antimony pentoxide is at least 35 percent, preferably 50 percent or more without gelation; (3) adding the concentrated phosphated sol to ethoxylated fatty acid amine; and (4) drying the resulting mixture to provide a colloidal antimony pentoxide powder having an adsorbed moisture content of no greater than 3.0 percent in order to provide the commercially available ADP 494 which is characterized as permitting at least 99.9 percent to pass through an 8 micron filter or, stated another way, in which 0.1 percent or less will not pass through this filter, thereby having improved dispersibility in a polar solvent. The antimony pentoxide powders are then employed to provide flame retardance by coating the textile or other article to be treated with a dispersion comprising the powder in a polar solvent, e.g. acetone, acrylonitrile, dimethylacetamide, methylethylketone, etc., and then drying to remove the solvent. In accordance with the patented invention, the presence of the phosphoric acid and the recited ethoxylated fatty acid amine in the colloidal powders is stated to be necessary to provide dispersibility in the polar solvent.
While the colloidal pentoxide powders described and claimed in U.S. Pat. No. 5,182,048 are completely satisfactory for use in the described manner and have in fact enjoyed commercial success, it has now been found that certain end users of the colloidal antimony pentoxide flame retardants manufactured and sold by Nyacol Products, Inc., assignee of this invention, require the pentoxide flame retardant be provided as a dispersion rather than as a powder.
The aforementioned U.S. Pat. No. 5,008,036 issued to Crompton et al. and assigned to Laurel Industries, Inc. is directed to colloidal dispersions of hydrous antimony pentoxide particles prepared by a process comprising introducing antimony metal or antimony trioxide into an essentially aqueous medium and contacting the antimony component with hydrogen peroxide to convert the antimony component to colloidal particles of antimony pentoxide. The step of contacting the antimony component with the peroxide may be done with or without the presence of an alkanolamine, alkanolamine salt, a-hydroxycarboxylic acid or polyhydroxy alcohol stabilizer. In Col. 4 useful alkanolamines are said to be water-soluble, e.g. diethanolamine and triethanolamine. In Col. 5 it is stated that the colloidal sols may be dried to a fine powder which may be redispersed to reform highly stable colloidal dispersions in an essentially aqueous media. In the paragraph bridging Cols. 5 and 6 it is recited that the colloidal dispersions are well suited for use in synthetic fibers and plastics because the particle size is from less than 40 .ANG. to approximately 300 .ANG. and the sols are compatible with many organic solvents which are useful for spinning and film casting of many polymers, including polyacrylonitrile, copolymers of acrylonitrile with vinyl and vinylidene halides, polyamides, polyesters, polyurethanes, polyacrylates, polyvinyl chloride, acrylonitrile-butadiene-styrene polymers, etc. Useful solvents are stated to include methanol, ethylene glycol, acetic acid, dimethylformamide, dimethylacetamide, formamide, trimethylolpropane, etc.
Example XI of the '036 patent is considered to be relevant as background information to the state of the art with respect to the present invention to be detailed hereinafter. As recited in this example, an aqueous solution of triethanolamine phosphate is first formed by mixing triethanolamine with phosphoric acid in water. Antimony trioxide and hydrogen peroxide are heated to reflux in a separate container and the triethanol phosphate solution was then added to the reaction mixture to form a colloidal dispersion of hydrous antimony pentoxide particles containing approximately 9% antimony, has an average particle size of less than 40 .ANG. and is stabilized with approximately 0.3 moles of the alkanolamine salt per mole of antimony.
Having disclosed above the prior art known to Applicant and having discussed the prior art believed most relevant to the present invention which will be described in detail hereinafter.
Stated simply, the task of this invention is to provide an aqueous dispersion of antimony pentoxide sol useful for flame retardancy and which is characterized as containing at least 50 percent by weight of the total dispersion of antimony pentoxide and most preferably at least 55 percent by weight of antimony pentoxide wherein the sol is characterized as being essentially free of agglomeration such that substantially all of the sol will pass through an 8 micron filter.